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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations consider whether AIR efficacy and den detection rates will be lower in areas adjacent to the Arctic National Wildlife Refuge because snow cover in these areas are greater than other areas and polar bear denning density is anticipated to be greater and more complex in these areas.
Response: We take into account in the model the fact that some dens inside ANWR will go undetected because AIR
surveys are not planned there and the area is outside of the activity area proposed by AOGA. We clearly stated this in the Proposed ITR document see page 29407 of the FR publication. We allow dens to be simulated in the refuge, even though activity does not occur there as part of this Request. But they were put there because they could be disturbed by activities in the petition area and go undetected by AIR. Any den within a mile of activity proposed in the ITR, but that occurred inside the refuge, was accounted for in our estimates of take. Because we account for these dens but assume that no AIR surveys will take place, differences in habitat conditions that could affect AIR
detection rates are not relevant.
Comment 123: One commenter suggested that the Service continue to evaluate and refine their polar bear denning model assumptions used to determine take estimates for their regulations as more data become available.
Response: The Service has used a comprehensive dataset of polar bear observations to develop estimates of Level B harassment, and will continue to refine these methods and our database for future ITRs. Comparing denning model results to historic Industrypolar bear encounter records is not possible because a systematic effort has never been undertaken by Industry to find all dens adjacent to existing infrastructure, not just ice roads and tundra travel routes as is the current requirement under the existing ITR.
Additionally, even when a den is found, monitoring has not occurred systematically or frequently to look at dates of den emergence and departure.
Further, given that the effects of early emergence can lead to lower cub survival, there is no way for Industry to document all cub mortality events that are associated with den disturbance as this would require constantly monitoring a family group until at least 100 days post emergence as Rode et al.
2018 did.
Comment 124: One commenter suggested that the polar bear den case studies used to determine responses to den disturbance do not accurately represent the polar bear responses
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expected during Industry activities because these case studies were collected during scientific studies in which polar bears were captured and collared.
Response: The goal of the case study analysis was to inform the consequences of den disturbance due to industrial activities. Including incidents spanning a range of activities i.e., Industry and research-related was reasonable as there are correlations between disturbance caused by research and that caused by Industry, such as inadvertently approaching a den at close distance. Additionally, the premise of some research was to evaluate the response of denning bears to remediation activities. Capture events likely are more intrusive than any disturbance related to industrial or other human activities and were not used in the calculation of take probabilities.
Bear responses to capture events can, however, help inform our understanding of how polar bears respond to any type of disturbance.
Other activities, such as disturbance caused by people approaching dens or accidental intrusion, are also possible when a dens location is unknown.
Consequently, exposures by researchers are useful in understanding how bears respond to disturbance and allowed us to better estimate the response probabilities that informed the simulation model.
Comment 125: One commenter suggested that the Services use of the upper 99 percent quantile of each probability distribution is too conservative to determine polar bear responses to disturbance and does not accurately reflect observer bias and the number of unobserved takes and this approach results in overestimation of polar bear incidental take.
Response: We disagree. The Service did not use the 99-percent quantiles to account for perceived directional bias by observers which can neither be confirmed nor denied due to lack of neutral third party observational data, instead, the Service used the 99-percent quantiles to encompass the number of potential Level B harassment events as directed by the MMPA.
Comment 126: One commenter suggested that the Service overestimated the take of polar bears during aircraft activities by assuming a lower flight altitude than is typically flown by Industry aircraft as part of their take determination analyses.
Response: When reviewing the dataset from coastal polar bear surveys, the Service found there was not enough data to identify a significant relationship between polar bear
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response and distance to the aircraft.
The Service applied a constant harassment rate to all flights listed as being flown at 1,500 ft AGL or lower.
Many flights were listed with a minimum altitude of 1,500 ft AGL, which would be within the scope of the analysis. Flights that are expected to be above 1,500 ft generally originating from outside of the ITR region were described as remaining at this altitude until descent. Without more information on each individual flights altitude, point of descent, and the present weather conditions, we made the assumption that an aircraft could descend to 1,500 ft AGL or less anywhere within the ITR region.
Comment 127: One commenter suggested that the Service overestimated the number of polar bears observed by vessels during in-water activities and this approach resulted in an overestimation of polar bear encounter rates and take estimates during offshore activities.
Response: There is no data to indicate the number of bears present in the water at any given time; however, we do have data for the number of bears located along the coast, which was used in the analyses. These bears frequently swim between barrier islands and may be impacted by these offshore activities.
Comment 128: One commenter suggested that the Service should reconsider whether the addition of new Industry facilities and infrastructure will correlate with an increase in incidental harassment of polar bears.
Response: We disagree. While AOGA
has drawn this conclusion in their Request, the relationship described by the Service between distance to shore and polar bear encounters indicates that an increase in coastal infrastructure will increase the number of encounters and subsequent harassment events. This issue was described at length within the proposed rule.
Comment 129: One commenter suggested that the Service should clarify how they accounted for the uncertainty of non-responses of polar bears to disturbance and whether the likely underrepresentation of non-responses may lead to overestimation of take by Level A harassment.
Response: The case study analysis included all well-documented records of human activity that occurred within 1.6 km of active polar bear dens. We do not believe that exposures that elicited detrimental responses were more likely to be documented than those that seemingly did not. Consequently, the probabilities of exposures resulting in lethal take or Level A harassment are unlikely to be biased. Further, cases that
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